Duchenne muscle plasma membrane has various ultrastructural abnormalities which can be demonstrated with freeze-fracture technique. There is a loss of intramembranous particles (IMP's) especially those IMP's which are clustered in orthogonal arrays. There is also increased complex formation with the sterol-specific ligand digitonin and an increase in membranous invaginations called caveolae. I plan to investigate these freeze-fracture abnormalities by attempting to reproduce them with specific perturbations in cultured fibroblasts and rat muscle in vivo. In fibroblasts I will study the effects of altered lipid content on both particle density and the extent of complex formation with digitonin. In rat muscle I will study the effects of transient denervation and artificial muscle damage on orthogonal arrays and caveolae. These experiments should increase understanding of the manifestations of Duchenne dystrophy at an ultrastructural level. I also plan to start a new investigation into the molecular genetics of Duchenne dystrophy. For this project I will isolate DNA from blood samples taken from patients with Duchenne dystrophy and their families. The DNA will be analyzed with probes that identify restriction fragment length polymorphisms linked to the Duchenne gene. This approach should help to characterize new probes and lead to the identification of those probes most closely linked to the defective gene.